Currently, traditional prognostic considerations include the patient’s age, TNM (tumor-lymph node-metastasis) stage, histological grading, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (c-erbB2 or HER2) status have been used as prognostic elements in breast cancer, but reliable and economical prognostic models are still lacking (D’Eredita’ et al., 2001). The gene discussed is ESR1; the disease is breast carcinoma.